Method for reconditioning used solutizer solutions



Q Patented Dec. 21, 1943 METHOD FOR RECONDITIONING USED SOLUTIZER SOLUTIONS Lawson E. Border, Alton, Ill., assignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Original application June 9, 1941,

Serial No. 397,212.

Divided and this application December 7, 1942, Serial No. 468,326

4 Claims.

,This invention is a division of my application, Serial No. 397,212, now Patent No. 2,315,480, filed June 9, 1941, and relates to the art of refini hydrocarbons by extraction with so-pcalled solu-- tizer solutions, more particularly to a method for reconditioning solutizer solution. Specifically, it

i concerned with a method for treating acontaminated solutizer solution with flocculent solids, whereby gums and resinous emulsifiers ar removed.

The solutizer process by means of which mercaptans and other weak organic acids contained in sour hydrocarbon distillates, and more particularly in gasoline distillates, are extracted with aqueous solution of alkali metal hydroxides containing solutizer is well known. (See references infra.)

Among the several compounds particularly suitable as solutizers for. weak organic acids are the following: aliphatic alkanolamines and amino alkylamines in which the alkylene radicals con- 'tain 2 to 3 carbon atoms; diamino alcohols, glycols and amino glycols of 3 to 5 carbon atoms; alkyl glycerines in which the number of carbon atoms in the alkyl radical is from 1 to 4; mono alkyl ethers of glycerine in which the alkyl radical has from 1 to 3 carbon atoms; diamino, dihydroxy, or amino hydroxy alkyl ethers, thioethers or imino ethers in which the alkyl radicals have" from 2 to 3 carbon atoms; alkali and particularly potassium salts of fatty acids having from 1 to 6 carbon atoms, or of amino r hydroxy fatty acids having from 3 to 7 carbon atoms, or of phenyl acetic acid, or of dicarboxylic acids having from to 11 carbon atoms in which the carboxyl radicals are separated by at least two carbon atoms, or of phenol or alkyl phenols; mixtures of the above and particularl mixtures with gum inhibitors soluble in aqueous caustic alkali solutions. Outstanding among the above are the salts, because in the regeneration of the spent solution containing absorbed weak organic acids by steam stripping, salts are substantially nonvolatile.

The solutizing process and the variou solut-izers enumerated also have been described in a series of patents and'patent applications, as well as in the general literature. for example, in the Yabrofl et al. United States Patents 2,149,379, 2,149,380, 2,152,166, 2,152,720, 2,152,723, 2,164,851, 2,186,398, 2,202,039, 2,223,798, and 2,229,995; Refiner and Natural Gasoline Manufacturer, May 1939, pages 1'71 to 1'76. and March 1940, pages '73 to 76'; Industrial and Engineering Chemistry, vol. 32, pages 257 to 262, February 1940; Chemical and Metallurgical Engineering, vol. 47, pages 7'76 to 778, November 1940; Oil and Gas Journal, vol. 39, No. 26, pages 55 to 56, November '7, 1940; etc.

In principle, a solutizer solution could be used indefinitely by continually regenerating it as by steaming. In practice, however, solutions used a long time tend to form relatively stable emulsions with the hydrocarbon oil under treatment probably due to gradual accumulation of emulsifiers believed to be resinous substances, which emulsions either reduce the throughput due to retarded settling or cause the carry-over of valuable solutizer. Coalescing the entrained droplets by contact with fine steel wool or other solids may not always remedy the situation. It is in such solutions used continuously and for a very long period in a solutizer plant that m reconditioning process is particularly useful.

, The exact source and chemical composition of the emulsifier are not known. It appears to be-a gummy material of a resinous nature. Possible sources of it include cracked gasoline feeds containing dissolved gums, oxidation of portions of solutizer solution such as alkyl phenols which may purposely form part of the solutizer solution or which may accumulate in solutizer solutions when cracked gasoline feeds are treated.

The object of this invention .is to facilitate the treatment of hydrocarbon distillates by means of'solutizer solutions. Another purpose is to decrease the costs of operation in solutizer plants by minimizing or preventing losses of valuable solutizer which are suffered when contaminated solutions must be discarded. Still another purpose is to decrease emulsion and foaming dimculties in solutizer plants. A more particular purpose is to provide a method for the removal from used solutizersolutions.

My invention is based on the discoverythat resinous emulsifiers which accumulate in used solutizer solutions may be removed by subjecting the said alkaline solutizer solution to a treatment with'fiocculent solids, thus rendering. said 40 solution clean and againsuitable for use in the solutizer-process for the extraction of mercaptans.

In carrying out my invention, a contaminate solutizer solution containing a resinous emulsifier is subjected to a treatment with flocculent solids, th flocculent material together with the resinous emulsifier and solids which are carried down by the flocs are separated, and the resulting clean solutizer solution is removed. ready to be reused.

By a contaminated solutizer solution I mean one containing an emulsifier which has slowly accumulated during the treatment and which is in solution or colloidally dispersed thereby causing said solution to have a tendency to form emulsions which may be relatively stable when it ismixed with gasoline in the course of the treatment or to foam excessively when the spent solution is being stripped thereby hampering the smooth operation of a solutizerplant.

The flocculent solids used in the process may of resinous emulsifiers and troublesome solids be either preformed or formed in situ.. By the aqueous solutions; by the latter, I mean those metal salts and hydroxides which form flocs when solutions or slurries of them are contacted with solutizer solutions. Suitable fioccular substances are less than 1% soluble in pure water at normal room temperature, are substantially inert under the conditions of the treatment, and are insoluble in relatively .concentrated alkali metal hydroxide. Particularly suitable are fioccular hydroxides of Mg, Ca, Cd, Cu, Cr, Fe, Ni, thecarbonates or phosphatesof the alkali earth metals and lead, and the sulfates of Ca, Ba and Pb when in fioccular form. Heavy metal sulfides in general do not readily formfiocs and therefore are usually less efiective.

Treatment with fiocs also includes treatments with solutions such as lime water, hard tap water, etc. which form fiocs when added to the contaminated solutizer solution. For example, hard tap water or lime water, i. e. saturated solution of slaked lime, when added to contaminated solutizer solution forms fiocs which carry down with them the resinous emulsifier and any of the troublesome solids present. f

Fiocs may also be produced by introducing a solution of water-soluble salt-which'will form a hydroxide floc when contacted with the concentrated alkaline solutizer solution. However, this method has the disadvantageof converting free KOH or NaOH of the solutizer solution to the corresponding salt, and therefore in general is less desirable.

The solution and the fiocs should be intimately contacted so as to cause the entrainment of the resinous emulsifier with the floc thereby-enabling the separation of the emulsifier from. the cleansed solutizer solution. Conventional methods oi. separation such as settling, decanting, filtering, etc.

are generally suitable. The contacting may be continuous or batchwise, and may be resorted to whenever the emulsifier content has built up to proportions which under the particular treating conditions in the plant may cause difilculties. In order to avoid slow or incomplete settling, two independent factors must be considered. They are dilution of solutizer solution and the quantity of tap water introduced. Solutizer solution at the time the .tap water is introduced should contain alkali metalhydroxide in a concentration preferably not greater than 3N. Thus, when starting out with solutizer solution which contains alkali metal hydroxide in-concentration of above 3N, such as about 6N as most frequently used, it is desirable to carry out any precipitation in a dilution of at least 1:1 solutizer solution to water. However, when using tap water, insurficient amounts of fioc may be formed atthis dilution. 8 to 10 parts of hard water per part of solutizer solution are normally required, which water should'preferably have a minimum hardan emulsion of the onesater type is formed and collects at the top oi the solutizer solution. A similar type of emulsion can be formed by stir- .ring solutizer solution and gasoline together, and

a stirrer test was accordingly devised whereby small amounts of solutizer solution and gasoline could be caused 'to form an. emulsion under con trolled conditions, and the time oi settling measured.

time (time necessary for separation of the two phases) was 20 minutes with a rag which persisted for over 30 minutes. Another portion of the same contaminated solutizer solution was diluted with about 10 parts of hard tap water. The

mixture was centrifuged for 10 minutes at 1500- R. P. M. and then filtered through a sintered glass filter. The filtered solution was then stirred with a full-range cracked gasoline and the settling time was found to be quite rapid, the solution appearing clear and bright.

I claim as my invention: l. A process for reconditioning a contamina aqueous alkali metal hydroxide solution containinga solutize'r for mercaptans, which solution was used to extract weak acids from a sour hydrocarbon distillate and regenerated by steam stripping whereby resinous emulsifiers-accumulated. in the aqueous solution, comprising contacting said aqueous solution with at least 8 volumes of tap water having a hardness of not less than 100 parts per million to entrain resinous emulsifier witli'the resultingfiocculent solid, separating said fiocculent solid containing entrained emulsifier from said solution, the latter having retained said solutizer for mercaptans, and reconcentrating.

2. A process for reconditioning a contaminated aqueous alkali metal hydroxide solution having a concentration of at least 3N which solution was used to extract weak a'cids irhm'a sour hydrocarbon distillate and regenerated by steam stripping whereby resinous emulsifiers accumulated in the aqueoussolution, comprising contacting said aqueous solution withat least 8 volumes 0! tap water having .a hardness of not less than 100 parts per million, to entrain resinous emulsifier with the resulting fiocculent solid, separating said fiocculent solid containing entrained emulsifier from said solution and reconcentrating.

3. The process of claim 2 wherein said solution is contacted with 8 to 10 volumes of tap water. 4. A process for purifying a contaminated aqueous alkali metal hydroxide solution containing-a; solutizer for mercaptans which solution was used to extract weak acids from a sour hydrocarbori distillate and regenerated by steam stripping whereby resinous emulsifiers accumulated in the aqueous solutiomcomprising contacting said aqueous solution with at least an equal volume of I tap water having a hardness of not less than A full-range cracked gasoline wasstlrred vigor- 

